Rats that inhaled ethanol vapors for 7 or 14 days underwent a withdrawal syndrome following removal from the inhalation chambers. Approximately 60% of rats exposed to the vapors for 3 days also exhibited various withdrawal symptoms, but rats exposed to vapors for 24 hours showed no marked withdrawal reaction. In a holeboard test performed approximately 11 hours after removal from the chambers, when blood alcohol concentrations were below the limits of detection, rats exposed to ethanol vapors for 24 hours or for 3, 7, or 14 days all had reduced exploratory and locomotor activities. Whether or not this hypoactivity is a manifestation of a withdrawal reaction or refects some other effect of exposure to ethanol vapors is currently under investigation.